METHOD OF FORGING A CRANKSHAFT

摘要

A method of forging a crank shaft at least including: a first step of forming a pair of fitting grooves in an outer periphery of a crank throw portion, said grooves extending perpendicular to an axis of the crank throw portion as well as to a diametral line thereof; a second step of subjecting said billet to rough forging by using a rough forging mold adapted to determine the position of the billet in cooperation with the fitting grooves of the crank throw portion and a journal portion, in which step, an outflow of burr is restricted by means of an inclined offset surface disposed opposite to the outflow direction of said burr while the crank throw portion is forced to move towards a crank pin position; and a third step of subjecting said billet to finish forging by using a finish forging mold, wherein burr is restricted its outflowing by an inclined offset surface disposed opposite to the outflow direction of the burr.